1. Field of the Invention
The present invention relates to Time Division Multiple Access (xe2x80x9cTDMAxe2x80x9d) controllers. More particularly, the present invention relates to a TDMA slot allocation unit for providing a versatile slot allocation/deallocation in the TDMA controller.
2. Background Information
Data networks which have significant packet propagation delay (i.e., the delay between the transmission of the data packet by a network node and its reception by another node) compared to a packet duration, require a Time Division Multiple Access (xe2x80x9cTDMAxe2x80x9d) controller that controls the time when the node is allowed to access the common media in the transmit mode. To stay synchronized, the TDMA controllers in the network nodes exchange messages. Accordingly, the TDMA controller functions include signal message reception, message interpretation and processing, and message execution.
The complexity of the modem TDMA protocols require the processor to process system messages and generate, among other things, control signals for the hardware. This results in variable delay if software is used for both message interpretation and control signal generation. Moreover, the behavior of the system using a host processor is much less predictable in a multi-tasking operating system because the host processor may not be able to provide the time critical transmit signals on time. One possible solution is to provide a separate processor dedicated to the TDMA controller. However, this yields in a cost increase which is undesirable.
For example, TDMA techniques are being applied to cable modems and several TDMA standards have been proposed for cable modem systems. These standards include IEEE 802.14, Digital Audio and Video Council (xe2x80x9cDAVICxe2x80x9d), and Multi-media Communication Network System (xe2x80x9cMCNSxe2x80x9d), to name a few. With different possible protocols, it is increasingly difficult to adapt to the different and often changing protocols without making changes to the hardware and to make cable modem products interoperable.
Accordingly, there is a need in the art for a TDMA controller which can perform time-critical tasks without an on-board processor and accommodate the changing specifications in the protocol without modification of the hardware.
The present invention is a versatile time division multiple access (xe2x80x9cTDMAxe2x80x9d) slot allocation unit. In one embodiment, the versatile TDMA slot allocation unit includes a slot counter configured to provide an address representative of a time slot and a slot descriptor table that contains one or more slot descriptors each of which describes an action that may be performed within the time slot. The slot descriptor table is configured to receive the address and provide the slot descriptor pointed to by the address. In addition, the TDMA slot allocation unit includes a slot descriptor decoder configured to decode the slot descriptor and provide one or more signals.